Studies and development of an organic electroluminescence device (hereinafter sometimes referred to as a “device” or an “organic EL device”) are being aggressively made, because high-luminance luminescence can be obtained by low-voltage driving. The organic electroluminescence device has an organic layer between a pair of electrodes, where the energy of an exciton produced when an electron injected from a cathode and a hole injected from an anode are recombined in the organic layer is utilized for luminescence.
In recent years, a phosphorescent material is used with an attempt to achieve high efficiency of the device. For example, an organic electroluminescence device enhanced in the luminous efficiency and durability by using an iridium complex or a platinum complex as the phosphorescent material is being studied. Also, a doping-type device using a light emitting layer where a light emitting material is doped in a host material is widely employed.
Patent Document 1: U.S. Patent Application Publication No. 2007/0297033 discloses a technique where an iridium or platinum complex with a ligand having a condensed ring structure is used as a phosphorescent material so as to obtain a high-durability device capable of emitting blue light with high color purity.
Also, Patent Document 2: Japanese Patent No. 4,039,023 discloses a method where a light emitting material incapable of high-efficiency luminescence by itself is caused to emit high-luminance light with high efficiency by using a method of incorporating a phosphorescent metal complex and another light emitting material together in the light emitting layer.